1. Field of the Invention
The present invention relates to a driving force control apparatus of a vehicle in which a single mode is selected from a plurality of modes having different driving force characteristics by external operation and a driving force instruction value is set according to the driving force characteristic of the selected mode.
2. Description of the Related Art
In a vehicle such as an automobile, it is preferable that fuel economy performance and driving performance (acceleration response) are both favorable in general, but it is difficult to satisfy both in a single vehicle. Therefore, a technology is known that a plurality of control modes such as an economy mode with an emphasis on fuel economy performance and a power mode with an emphasis on output are set in addition to a normal mode and one control mode is selected by operation of a switch or the like by a driver so that both the fuel economy performance and driving performance are satisfied in a single vehicle.
In Japanese Patent Laid-Open Publication No. 5-332236, for example, a technology is disclosed that an air-fuel ratio map and an ignition timing map corresponding to the control mode (either one of the economy mode and the power mode) selected by a driver are selected so that fuel injection control and ignition timing control are carried out based on the selected map.
In the technology disclosed in the above document, when a driver chooses a specific mode, an engine output is controlled according to the mode selected by the driver after the selection till the driver switches the mode to another one.
However, if the driver chooses a mode with an emphasis on output such as a power mode at cold start, there is nonconformity that fuel economy performance and exhaust emission are deteriorated in warm-up driving after the start. Similarly, if a mode with an emphasis on output such as a power mode is selected at reverse driving, there is a problem that fine accelerator control at a low speed is difficult and operability is poor.
As above, even in a vehicle capable of selection from a plurality of modes, there are cases where control of a vehicle based on the mode selected by a driver is not favorable from the viewpoint of use environment of the vehicle and operating feeling of the driver.
As a measure against the problem, during warm-up driving and reverse driving, a mode with an emphasis on output such as a power mode may be limited, but limitation on mode switching gives a sense of discomfort to the driver.